Transoral robotic surgery for the resection of parapharyngeal tumour: Our experience in ten patients

Abstract

Dear Editor, Treatment for parapharyngeal tumours involves surgery, and different surgical approaches have been reported in the literature, including the transcervical, transcervical-transparotid and transmandibular approaches.1–3 However, these invasive procedures had a risk of comorbidities and left a visible scar on the face or neck. The transoral approach among various conservative methods is under active research and clinical utilisation. Many studies have demonstrated the feasibility of transoral robotic surgery in the treatment of laryngopharyngeal tumours with excellent results in terms of oncologic radicality and functional preservation.4–6 Previous reports already showed the feasibility of transoral robotic surgery for the resection of parapharyngeal space tumour in selected cases.7,8 We recently refined the transoral extirpation of parapharyngeal tumours using the da Vinci robot system (Intuitive Surgical Inc., Sunnyvale, CA, USA). We used this approach alone or in combination with the transparotid approach depending on the localisation of the tumour. The purpose of this study was to analyse the validity of this technique. We performed transoral parapharyngeal tumour resection in 10 patients. Main clinical features are reported in Table 1. Patient ages ranged from 25 to 56 years (mean = 39.2). Pre-operative imaging studies evaluated the lesions of the patients (Fig. 1). They were followed up for a mean period of 20 months (range, 8–33) after the procedure. The operating room and da Vinci Robotic system were set up as described in a previous study.4–6 According to the dimension and localisation of the lesion, we classified surgical techniques into three classes: Type 1: Robotic transoral resection. This approach was used in three cases (patient 1, 8 and 9) of parapharyngeal tumour with limited dimension, which did not extend or push towards the stylomandibular tunnel (Fig. 2a). In these cases, a vertical incision was made on the mucosa covering the lesion (Fig. 2c). Then, the mass was evidenced and gently detached from the soft surrounding tissues without capsular interruption (Fig. 2d). Vascular structures were isolated and managed through vessel clipping or simple ligation (Fig. 2e). The incision was sutured using the robotic arms through simple ligation (Fig. 2f). Type 2: Robotic transoral resection with coblation using a coblator (Coblator II Surgery System, ArthroCare ENT, Austin, Texas, USA). This approach was used in cases (patient 2 and 7) of larger parapharyngeal tumours originated from the parapharyngeal space and pushed towards the stylomandibular tunnel (Fig. 3a). A vertical incision was made on the mucosa covering the lesion. Afterwards, the mass was evidenced and gently detached from the soft surrounding tissues without capsular interruption (Fig. 3a,d). In these cases, to complete the resection without risk of injury, the tumour capsule was incised and a coblator was inserted into the tumour (Fig. 3b,e). The volume of the mass was reduced, and the excision was completed transorally, according to the modalities of the Type 1 technique reported above (Fig. 3c,f). Coblation of the central portion allowed the surgeon to reduce the dimensions of the mass to obtain better control of the neurovascular structures. The reason why we used the coblator is to reduce the volume of the tumour mass. This instrument allowed a gentle debulking of the tumour inner mass. Furthermore, the small dimension of the instrument permitted controlling the movements of its sharp tip in all the phases of the procedure. Once the volume of the tumour is reduced, we could meticulously suture the capsule and completed the extra-capsular dissection without risk of tumour spillage. Type 3: Robotic transoral resection plus transparotid resection. This approach was used in five cases (patient 3, 4, 5, 6 and 10) of bilobed large tumours that originated from the deep lobe of the parotid gland and extended through the stylomandibular tunnel into the parapharyngeal space (Fig. 4a). In these cases, the lateral part of the tumour was detached from the soft tissues via a transparotid approach (Fig. 4b). The excision was completed with a daVinci robotic system via a transoral approach (Fig. 4c). Based on histopathologic evaluation, eight patients were diagnosed with pleomorphic adenoma and two patients were diagnosed with schwannoma. The mean robotic operative time was 113 min (range, 52–182) and that for the setting of the robotic system was 8 min (range, 6–10). In all patients, parapharyngeal tumour resection was completed successfully. No functional deficits because of nerve injuries were observed in all of the patients. Nasogastric feeding tubes were removed after a mean of 10 days (range, 5–15), and all patients returned to a regular diet thereafter. There were no significant complications in all the patients. We did not observe orocervical fistulas in the Type 3 resections. The average blood loss during the operation was 22 mL (range, 5–50). First, images obtained by the endoscopic arm equipped with two integrated cameras allowed us to three-dimensionally analyse and preserve the delicate anatomic structures of the parapharyngeal space. Using the robot, we were able to maintain an optimal bleeding control. Parapharyngeal space is an area rich in vascular structures including the internal carotid artery, internal maxillary artery and their branches. We were able to easily identify and manage these vessels, especially those located posterior to the tumour. Furthermore, the da Vinci robotic system can perform movements whose excursion quality and quantity are higher than those achievable with the human hand. Using these advantages, the robotic surgical system can remove the tumour en-bloc, preserving the capsule and surrounding anatomical structures. Compared to other open techniques, transoral robotic surgery results in better cosmetic results. No visible scars were present, especially compared with the transmandibular approach. Even the transoral approach plus transparotid approach resulted in a better cosmetic result, as a modified facelift incision was used. The average period of follow-up for the patients was 20 months (range, 8–33 months). Post-operative CT scans showed no recurrences in the patients (Fig. 1), and no recurrences were observed at the last follow-up. All patients were satisfied with their cosmetic outcomes. However, we thought that an average of 20 months was not enough to declare cure from disease because pleomorphic adenomas can recur several years later. Therefore, we are planning to follow up our patients for several years and report their long-term outcomes. Surgical approaches to the parapharynx should meet two criteria: wide intra-operative visibility for safe radical dissection or minimal functional or cosmetic after-effects.9 Malone et al. and Hamza et al. reported on parapharyngeal tumour resections using the transcervical approach in the majority of their cases.1,2 Hughes et al.3 published a series of 172 cases using the transcervical and transparotid approaches in 94% of cases, while mandibular osteotomy was required in only 2% of cases. The transmandibular approach, alone or in combination with the other approaches mentioned above, is used when wide exposure is needed as well as in cases of benign but large tumours. However, comorbidities of disfigurement, swallowing difficulties and long post-operative recovery are a concern with the latter. We recently refined transoral resection of parapharyngeal tumour using the da Vinci robot system. We used this approach alone or in combination with the transparotid approach depending on the localisation and dimension of the tumour. These surgical techniques have clear advantages. Certainly, the main incentive is optimal bleeding control. Parapharyngeal space is an area rich in vascular structures including the internal carotid artery, internal maxillary artery and their branches. Using the robot, we were able to easily identify and manage the vessels, especially those located posterior to the tumour. The bloodless field allowed the surgeon to conduct a safe and precise excision of the mass. Another clear advantage is the absence of a visible scar on the neck. In fact, conventional techniques include cervical incisions that cause disfigurement, as the scar may be visible even after many years. Even in cases of huge parapharyngeal lesions pushing towards the stylomandibular tunnel (Type 2), we were able to complete the excision transorally through coblation of tumour using a coblator. Also, in Type 3 resections, we used a modified facelift incision to reach the tumour on the lateral side. In these cases, the incision line was very close to the hairline and obviously more cosmetically acceptable than a traditional cervical incision. As for limitations, the surgical costs of transoral robotic surgery are actually higher than conventional surgery. The surgical team must have expertise and be composed of at least two people. The cost of the da Vinci robotic system is high, but it can be used for many other types of surgery.4–6 Moreover, these devices, to be used correctly, constitute a considerable learning curve for both the surgeon and his assistant. Therefore, at the beginning, this can significantly affect operation time. Transoral robotic surgery for the resection of parapharyngeal tumours is technically feasible and secures better cosmetic outcomes than the conventional approaches. We think that, using the robot, the limitations imposed by the conventional transoral approach are easily overcome, possibly expanding its indications for more aggressive diseases of the parapharyngeal space. None declared.